drivers/infiniband/core/ucma.c in the Linux kernel through 4.17.11 allows ucma_leave_multicast to access a certain data structure after a cleanup step in ucma_process_join, which allows attackers to cause a denial of service (use-after-free). http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-14734
